I don't know what this is, or when this will happen, maybe it'll be a NYCC announcement, who knows... but all I know is that I want this.
What am I talking about? Well, this tweet should explain that quite clearly.
just got confirmation pal @Sean_G_Murphy and I can do a short Batman sci-fi future story for something special coming up - excited
— Scott Snyder (@Ssnyder1835) October 3, 2013
Maybe this is something like Legends of the Dark Knight? But you'd think it'd be a bigger venue given the creators attached... Perhaps one of those weekly, rotating creator books Bleeding Cool has mentioned a couple of times? Or something completely crazy and different.
UPDATE (10/10): Turns out it's part of Detective Comics #27